Light-emitting device, distance-imaging device, and monitoring device

Abstract

A plurality of light sources (21) emit light containing a non-visible wavelength band. A housing (28) demarcates at least a portion of the space in which the plurality of light sources (21) are accommodated. The housing (28) has a light transmission portion (281) that allows the passage of light in the non-visible wavelength band and blocks the passage of light in a visible wavelength band.

Description

Light emitting device, distance imaging device, and monitoring device

[0001] The present disclosure relates to a light emitting device including a plurality of light sources that emit light used for distance imaging. The present disclosure also relates to a distance imaging device and a monitoring device that include the light emitting device.

[0002] Patent Document 1 discloses a range imaging device mounted on a vehicle, which is an example of a monitoring device. The range imaging device includes a light emitting device, an imaging device, and a computing device. The light emitting device emits light toward an area located in front of the vehicle, which is an example of a monitoring area. The imaging device captures an image of an object located in the area based on the light reflected by the object. The computing device calculates the distance to the object based on the time between when light is emitted from the light emitting device and when the light is incident on the imaging device.

[0003] Japanese Patent Application Publication No. 2009-257983

[0004] There is a demand for reducing the burden of optical design in order to improve the light distribution of light emitted from a light-emitting device having a plurality of light sources.

[0005] A first example embodiment that can be provided by the present disclosure is a light-emitting device comprising: a plurality of light sources that emit light including a non-visible wavelength range; and a housing that defines at least a portion of a space in which the plurality of light sources are housed, wherein the housing has a light-transmitting portion that allows light in the non-visible wavelength range to pass through and blocks light in the visible wavelength range from passing through.

[0006] A second example embodiment that can be provided by the present disclosure is a distance imaging device, comprising: a light emitting device according to the first example embodiment; an imaging device that acquires an image of a subject based on the light reflected by the subject; and a computing device that calculates the distance to the subject based on the time from when the light is emitted from the light emitting device to when the light is incident on the imaging device.

[0007] A third example embodiment that can be provided by the present disclosure is a monitoring device that includes the distance imaging device according to the second example embodiment and causes the light emitting device according to the first example embodiment to emit light toward a predetermined monitoring area.

[0008] Multiple light sources are used to provide light for information acquisition over a wider surveillance area. Because the emission spectra of elements used as light sources typically vary slightly, the more light sources used, the greater the probability that the spectrum of the combined light that forms the final light distribution pattern will contain components that deviate from the desired characteristics. If such components are unexpectedly included in the visible wavelength range, there is a risk that the light emitted from the light-emitting device will be visible to people within the surveillance area, even though distance imaging using invisible light is intended. While one possible solution to address the variation in emission spectra between elements is to use elements that emit light at central wavelengths farther from the visible wavelength range as light sources, such elements are generally more difficult to obtain than elements that emit light at central wavelengths closer to the visible wavelength range.

[0009] According to the configurations of the above-described embodiments, even if the light unexpectedly contains visible wavelength components due to variations in the light-emitting characteristics of the elements used as the multiple light sources, the wavelength selectivity of the light-transmitting portion of the housing allows only light in the invisible wavelength range to reach the monitored area. This increases the degree of freedom in selecting the elements used as the multiple light sources, thereby reducing the burden of optical design to improve the light distribution of light emitted from a light-emitting device having multiple light sources.

[0010] 1 illustrates an example of the functional configuration of a range imaging device according to an embodiment. An example of a vehicle equipped with the range imaging device of FIG. 1. An exploded perspective view illustrating the configuration of the light emitting device of FIG. 1. A front view illustrating the optical member of FIG. 3. A rear view illustrating the optical member of FIG. 3. An example of a cross section taken along line VI-VI in FIG. 4 as viewed from the direction of the arrows. A cross-sectional view illustrating the configuration of the light emitting device of FIG. 1. An example of the appearance of the housing as viewed from the front. An example of the appearance of the housing as viewed from the direction of arrow IX in FIG. 8. An example of the appearance of the housing as viewed from the direction of arrow X in FIG. 9. An example of a light distribution pattern formed by light passing through the light-transmitting portion of FIG. 7. An example of a light distribution pattern formed by light passing through the light-transmitting portion according to a first comparative example. An example of a light distribution pattern formed by light passing through the light-transmitting portion according to a second comparative example.

[0011] The following detailed description of exemplary embodiments will be given with reference to the accompanying drawings. In the drawings used in the following description, the scale has been changed as necessary to make each component recognizable.

[0012] In the accompanying drawings, arrow F indicates the forward direction of the illustrated structure. Arrow B indicates the rearward direction of the illustrated structure. Arrow U indicates the upward direction of the illustrated structure. Arrow D indicates the downward direction of the illustrated structure. Arrow R indicates the rightward direction of the illustrated structure. Arrow L indicates the leftward direction of the illustrated structure. These directional expressions are used for convenience of explanation and do not limit the posture or direction of the illustrated structure in actual use.

[0013] The term "front-rear direction" used in this specification means a direction along the aforementioned front and rear directions. The term "up-down direction" used in this specification means a direction along the aforementioned top and bottom directions. The term "left-right direction" used in this specification means a direction along the aforementioned left and right directions.

[0014] The expression "extending in the front-to-rear direction" used in this specification includes extending at an angle relative to the front-to-rear direction, and means extending at an angle closer to the front-to-rear direction than the up-down and left-to-right directions.

[0015] The expression "extending in the vertical direction" used in this specification includes extending at an angle relative to the vertical direction, and means extending at an angle closer to the vertical direction than the front-to-back and left-to-right directions.

[0016] The expression "extending in the left-right direction" used in this specification includes extending at an angle relative to the left-right direction, and means extending at an angle closer to the left-right direction than the front-back and up-down directions.

[0017] 1 illustrates an example of the functional configuration of a range imaging device 1 according to one embodiment. The range imaging device 1 is a device that not only acquires an image IM in which a subject SB located within a subject area A is captured, but also acquires distance information to the subject SB.

[0018] The range imaging device 1 includes a light emitting device 2. The light emitting device 2 includes a light source that emits light L toward a subject area A. Examples of the light source include semiconductor light emitting elements such as light emitting diodes (LEDs) and laser diodes (LDs).

[0019] The distance imaging device 1 includes an imaging device 3. The imaging device 3 includes a light receiving element that outputs a signal corresponding to light arriving from a subject area A. An example of the light receiving element is a CMOS image sensor. The imaging device 3 is configured to capture an image of the subject SB based on light L reflected by the subject SB.

[0020] The range imaging device 1 includes a calculation device 4. The calculation device 4 is configured to calculate the distance to the subject SB based on the time from when light L is emitted from the light emitting device 2 until the light L is incident on the imaging device 3. A time of flight (TOF) method is used to calculate the distance. Either a direct TOF method or an indirect TOF method may be used. The TOF method itself is well known, so a detailed description thereof will be omitted.

[0021] As illustrated in Figure 2, the range imaging device 1 can be mounted on a vehicle 5. The position of the range imaging device 1 on the vehicle 5 is determined appropriately depending on the position of the subject area A. In this example, the range imaging device 1 is mounted on the right front corner of the vehicle 5. This makes it possible to monitor the subject area A set around the right corner of the vehicle 5. For example, the presence or absence of an object OB that requires the vehicle 5 to take avoidance action can be monitored. The vehicle 5 is an example of a moving body. The vehicle 5 is an example of a monitoring device. The subject area A is an example of a monitored area.

[0022] 3 , the light-emitting device 2 includes a plurality of light sources 21. The plurality of light sources 21 are arranged to form a two-dimensional array. Each of the plurality of light sources 21 is configured to emit light used for distance imaging. In this embodiment, the light used for distance imaging includes an infrared wavelength range. In other words, the light used for distance imaging includes a non-visible wavelength range.

[0023] The light-emitting device 2 includes electronic components 22. The electronic components 22 include various elements associated with the operation of the light sources 21. Examples of such elements include a switching element that controls the turning on and off of each of the multiple light sources 21, a temperature sensor that detects the temperature of the area where the multiple light sources 21 are arranged, and the like.

[0024] The light-emitting device 2 includes a shielding member 23. The shielding member 23 is disposed so as to block spatial conduction of noise to the electronic components 22. The noise includes electromagnetic noise and electrostatic noise. The shielding member 23 can be formed from a conductive material.

[0025] The shield member 23 has a plurality of openings 231. The plurality of openings 231 are arranged to form a two-dimensional array. The number of the plurality of openings 231 matches the number of the plurality of light sources 21. In other words, each of the plurality of openings 231 corresponds to one of the plurality of light sources 21.

[0026] The light-emitting device 2 includes an optical member 24. Fig. 4 illustrates an example of the appearance of the optical member 24 as viewed from the front. Fig. 5 illustrates an example of the appearance of the optical member 24 as viewed from the back. The back of the optical member 24 faces the shield member 23. Fig. 6 illustrates an example of a cross section of the optical member 24 as viewed from the direction of the arrow along line VI-VI in Fig. 4.

[0027] 5 and 6 , the optical member 24 includes a plurality of lenses 241. The plurality of lenses 241 are arranged to form a two-dimensional array. The plurality of lenses 241 are configured to allow the passage of light emitted from the plurality of light sources 21. The number of the plurality of lenses 241 matches the number of the plurality of openings 231. That is, each of the plurality of lenses 241 is associated with one of the plurality of openings 231 and one of the plurality of light sources 21.

[0028] 3, 4, and 6, the optical member 24 has an exit surface 242. The exit surface 242 has minute irregularities formed thereon, which are configured to scatter the light that has passed through the multiple lenses 241. As a result, light L is obtained as composite light emitted from the light-emitting device 2.

[0029] 3 , the light emitting device 2 includes a circuit board 25. The plurality of light sources 21 and the electronic components 22 are mounted on a common circuit board 25. The plurality of light sources 21 and the electronic components 22 are electrically connected through circuit wiring formed on the circuit board 25. The shielding member 23 is disposed between the optical member 24 and the circuit board 25, and allows the passage of light L0 through the plurality of openings 231 while blocking noise from reaching the electronic components 22.

[0030] The light emitting device 2 includes a heat dissipation member 26. The heat dissipation member 26 is a component for dissipating heat generated from the plurality of light sources 21 and the electronic components 22. The heat dissipation member 26 includes a plurality of fins 261 for promoting heat dissipation.

[0031] The light emitting device 2 includes a fastening member 27. The fastening member 27 is a component for fastening the shielding member 23, the optical member 24, and the circuit board 25 to the heat dissipation member 26. The fastening member 27 has a head portion 271 and a shaft portion 272. The fastening member 27 can be, for example, a screw having a thread formed in the shaft portion 272.

[0032] A first through hole 251 is formed in the circuit board 25. A second through hole 232 is formed in the shielding member 23. A third through hole 243 is formed in the optical member 24. The circuit board 25, the shielding member 23, and the optical member 24 are arranged in this order from the heat dissipation member 26 side so that the first through hole 251, the second through hole 232, and the third through hole 243 are arranged concentrically.

[0033] 7 , the fastening member 27 is attached from the side of the optical member 24 so that the shank 272 is positioned in the first through hole 251, the second through hole 232, and the third through hole 243. When the shank 272 is screwed into the receiving portion 262 formed in the heat dissipation member 26, the head portion 271 presses the optical member 24 toward the heat dissipation member 26. Accordingly, the shield member 23 and the circuit board 25 are also pressed toward the heat dissipation member 26, and are fastened together.

[0034] The light-emitting device 2 includes a housing 28. The housing 28 defines a space in which a plurality of light sources 21 are housed together with a heat dissipation member 26. FIG. 8 illustrates an example of the appearance of the housing 28 as seen from the front. FIG. 7 corresponds to a cross section taken along line VII-VII in FIG. 8 as seen from the direction of the arrows. FIG. 9 illustrates an example of the appearance of the housing 28 as seen from the direction of arrow IX in FIG. 8. FIG. 10 illustrates an example of the appearance of the housing 28 as seen from the direction of arrow X in FIG. 9.

[0035] 7 , the housing 28 has a light-transmitting portion 281. The light-transmitting portion 281 is disposed at a position that allows the passage of light L emitted from the plurality of light sources 21. In other words, the light-transmitting portion 281 is disposed on an extension of the optical axis AX of each light source 21.

[0036] The light-transmitting portion 281 is configured to allow light in the invisible wavelength range to pass through and block light in the visible wavelength range to pass through. The light-transmitting portion 281 may be realized by forming the housing 28 from a material having wavelength selectivity, or by forming a layer having wavelength selectivity on the surface of the housing 28 made of a material that allows light in the visible wavelength range to pass through.

[0037] Multiple light sources 21 are used to supply light L for distance imaging to a wider subject area A. Since the emission spectra of elements used as light sources 21 generally vary slightly between elements, the more light sources 21 used, the higher the probability that the spectrum of the combined light that forms the final light distribution pattern will contain components that deviate from the desired characteristics. If such components are unexpectedly included in the visible wavelength range, there is a risk that the light L emitted from the light-emitting device 2 will be visible to people within the subject area A, even though distance imaging using invisible light is intended. One possible measure to compensate for the variation in the emission spectra between elements is to use elements that emit light at central wavelengths farther from the visible wavelength range as light sources, but such elements are generally more difficult to obtain than elements that emit light at central wavelengths closer to the visible wavelength range.

[0038] According to the configuration of this embodiment, even if light L unexpectedly contains visible wavelength components due to variations in the light emission characteristics among the elements used as the multiple light sources 21, the wavelength selectivity of the light-transmitting portion 281 of the housing 28 allows only light in the invisible wavelength range to reach the subject area A. Since the degree of freedom in selecting the elements used as the multiple light sources 21 can be increased, the burden of optical design for improving the light distribution of light L emitted from the light-emitting device 2 having the multiple light sources 21 can be reduced.

[0039] In addition, the expression "improving the light distribution of light emitted from the light-emitting device" used in this specification not only means making the light distribution pattern formed by the light L actually emitted from the light-emitting device 2 closer to the desired shape, but also means reducing the components contained in the emitted light L that deviate from the desired wavelength range.

[0040] The configuration according to this embodiment is particularly useful when the visible wavelength component is in the red wavelength range. When the subject area A is set in front of the vehicle 5 as illustrated in Fig. 2, the light-transmitting portion 281 of the housing 28 can block the emission of red light in the forward direction of the vehicle 5, which is subject to legal restrictions.

[0041] 7 and 10 , the optical axis AX of the light source 21 extends in the front-to-rear direction of the light-emitting device 2. The light-transmitting portion 281 of the housing 28 has a portion that extends in the up-down direction, perpendicular to the optical axis AX. The up-down direction is an example of the first direction.

[0042] The advantages of such a configuration will be described with reference to Figs. 11 to 13. Fig. 11 illustrates the contour shape of a light distribution pattern formed by light L passing through light-transmitting portion 281 of housing 28 according to this embodiment. Fig. 12 illustrates the contour shape of a light distribution pattern formed by light L passing through light-transmitting portion 281' of housing 28' according to a first comparative example. Fig. 13 illustrates the contour shape of a light distribution pattern formed by light L passing through light-transmitting portion 281" of housing 28" according to a second comparative example.

[0043] In each diagram showing a light distribution pattern, the numbers on the horizontal axis represent the horizontal deviation angle from the direction in which the optical axis AX of the light source 21 extends, when the direction is set to 0°. The numbers on the vertical axis represent the vertical deviation angle from the direction in which the optical axis AX of the light source 21 extends, when the direction is set to 0°.

[0044] 12 , the light-transmitting portion 281′ according to the first comparative example faces diagonally downward with respect to the horizontal plane. That is, the light-transmitting portion 281′ diagonally intersects with the optical axis AX of the light source 21. The shape of the light distribution pattern formed by the light L that has passed through the light-transmitting portion 281′ is shifted upward with respect to the horizontal axis.

[0045] As illustrated in FIG. 13 , the light-transmitting portion 281″ according to the second comparative example faces diagonally downward with respect to the horizontal plane. In other words, the light-transmitting portion 281″ intersects the optical axis AX of the light source 21 diagonally. The shape of the light distribution pattern formed by the light L that has passed through the light-transmitting portion 281″ is shifted downward with respect to the horizontal axis.

[0046] 11, the light distribution pattern formed by the light L passing through the light-transmitting portion 281 according to this embodiment, which extends in the vertical direction perpendicular to the optical axis AX, has a shape that is approximately symmetrical with respect to the horizontal axis. This fact means that there is no significant change in the light distribution characteristics even if the light-emitting device 2 is placed upside down.

[0047] For example, when the light-emitting device 2 is disposed in the right front corner of the vehicle 5 as illustrated in Fig. 2, the first horizontal wall 282 and the second horizontal wall 283 of the housing 28 illustrated in Fig. 8 face upward and downward, respectively. When the light-emitting device 2 is positioned so that the first horizontal wall 282 and the second horizontal wall 283 face downward and upward, respectively, it can obtain the same light distribution characteristics as the light-emitting device 2 disposed in the right front corner, even when it is disposed in the left front corner of the vehicle 5 as illustrated in Fig. 2.

[0048] Therefore, when multiple light-emitting devices 2 are arranged at positions symmetrical with respect to an axis of symmetry SA extending in the longitudinal direction of the vehicle 5, there is no need to vary the specifications of the light-emitting devices 2 for each position. In other words, light-emitting devices 2 with common specifications, each equipped with a housing 28 having a light-transmitting portion 281 extending in a first direction perpendicular to the optical axis AX of the light source 21, can be arranged at multiple positions symmetrical with respect to the axis of symmetry extending in the direction along the optical axis AX in a second direction perpendicular to the first direction. This makes it possible to suppress increases in manufacturing costs and management costs.

[0049] As illustrated in Figures 7 to 10, the housing 28 has an asymmetric shape in the left-right direction. The left-right direction is an example of a second direction. As illustrated in Figure 7, the light-transmitting portion 281 of the housing 28 obliquely intersects the optical axis AX of the light source 21 in the left-right direction. However, as can be seen from a comparison of the light distribution patterns illustrated in Figures 11 to 13, the influence of this configuration on the shape of the light distribution pattern is negligible compared to the influence in the up-down direction. Therefore, a shape of the housing 28 that is highly compatible with or compatible with the design of the vehicle 5 on which it is installed is permitted.

[0050] The above-described embodiments are merely examples for facilitating understanding of the present disclosure. The configurations according to the above-described embodiments may be appropriately modified or combined without departing from the spirit of the present disclosure.

[0051] The light emitting device 2, the image capturing device 3, and the processing device 4 that make up the distance imaging device 1 do not need to be housed in a common housing. At least one of the image capturing device 3 and the processing device 4 can be mounted at an appropriate position on the vehicle 5 independently of the light emitting device 2.

[0052] The range imaging device 1 can also be mounted on a moving body other than the vehicle 5. Examples of other moving bodies include trains, flying bodies, aircraft, ships, etc. The moving body may not require a driver. The moving body is also an example of a monitoring device.

[0053] The range imaging device 1 does not need to be mounted on a moving object. As an example, the range imaging device 1 can be mounted on transportation infrastructure equipment such as street lights and traffic lights. In this case, the subject area A can be set to include the road. As another example, the range imaging device 1 can also be applied to a security system installed in a house or facility to detect an object that enters the subject area A.

[0054] The light L emitted from the light-emitting device 2 does not necessarily need to be used for distance imaging. For example, the light-emitting device 2 having the above-described configuration can be used to emit light in the invisible wavelength range used in a LiDAR (Light Detection and Ranging) sensor that measures the distance to an object.

[0055] At least one of the shielding member 23 and the optical member 24 may be omitted depending on the application in which the light-emitting device 2 is used. The contents of Japanese Patent Application No. 2021-129920 filed on August 6, 2021 are incorporated by reference as part of this disclosure.

Claims

1. A plurality of light sources that emit light including a non-visible wavelength region, A housing that partitions at least a part of the space in which the plurality of light sources are accommodated, And is provided with, The housing has a light-transmitting portion that allows light in the non-visible wavelength region to pass through and blocks light in the visible wavelength region. Light-emitting device.

2. The visible wavelength region is a red wavelength region. The light-emitting device according to claim 1.

3. The light-transmitting portion has a portion that extends in a first direction orthogonal to the optical axis of each of the plurality of light sources. The light-emitting device according to claim 1.

4. The housing has an asymmetric shape with respect to a second direction orthogonal to the optical axis and the first direction. The light-emitting device according to claim 3.

5. The light-emitting device according to any one of claims 1 to 4, An imaging device that acquires an image of the subject based on the light reflected by the subject, An arithmetic device that calculates the distance to the subject based on the time from when the light is emitted from the light-emitting device until the light enters the imaging device, And is provided with, Distance imaging device.

6. Comprising the distance imaging device according to claim 5, and causing the light-emitting device to emit the light toward a predetermined monitoring region. Monitoring device.

7. A moving body. The monitoring device according to claim 6.